Turning water into a high density slurry ?

Not sure how the powder get to the top of the hill as pumping it back up must obey the First Law.

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Edited 21 hours ago21 hr by studiot

It’s offered as energy storage, so it’s pumped storage with a higher density than water. No 1st law issues.

not sure what advantage us gained by increasing the density of the water to a slurry.
Sure, you can use a lower height for storage, but the pumping load increases proportionately with the increase in density.
I haven't done, or seen, calculations so I'm not sure of any benefits other than convenience of using existing geological formations.

1 hour ago, MigL said:

not sure what advantage us gained by increasing the density of the water to a slurry.

The main advantage IS being able (potentially) to locate high capacity gravity storage in areas of lower relief, perhaps locating them closer to regions of high demand cutting distribution losses.

A secondary benefit maybe the lower liquid head to volume flow ratio may better facilitate the use of mixed flow (Francis vane type) pumps and turbines which may help hydraulic efficiency.

No mention of the high rates of mechanical wear typically associated with slurries though.

The fact and figures offered are few and far between.

However I did notice that they were talking about a slurry of density slightly greater than 2.

The only experience I have of pumping anything like that is for cementitious materials which have a density in the range 1.8 to 2.8.

The problem I worrry about is the flow rate/ fluid velocity.

It is not only mass that is important for generators attached to turbines, fluid velocity is also important.

Will pushing the slurry up to a high enough velocity not add to the unrecoverable energy costs ?

That is how fast will it flow back under gravity against pipe friction ?

6 hours ago, studiot said:

It is not only mass that is important for generators attached to turbines, fluid velocity is also important.

Will pushing the slurry up to a high enough velocity not add to the unrecoverable energy costs ?

For the same unit power output per unit volume of fluid, a denser fluid needs: less elevation difference; shorter pipe runs; lower fluid velocity.

Without knowing the exact nature of the fluid, it's impossible to say whether losses would rise or fall. For some dense fluids (e.g. mercury) I imagine that losses could fall significantly.

There is potential to increase power output per unit volume of fluid, but now losses would rise in rough proportion (also to square of velocity) though this does seem to imply that efficiency doen't take a serious hit.

Key algebra is h = v²/2g = 'velocity head'

Edited 2 hours ago2 hr by sethoflagos

43 minutes ago, sethoflagos said:

For the same unit power output per unit volume of fluid, a denser fluid needs: less elevation difference; shorter pipe runs; lower fluid velocity.

Without knowing the exact nature of the fluid, it's impossible to say whether losses would rise or fall. For some dense fluids (e.g. mercury) I imagine that losses could fall significantly.

There is potential to increase power output per unit volume of fluid, but now losses would rise in rough proportion (also to square of velocity) though this does seem to imply that efficiency doen't take a serious hit.

Key algebra is h = v²/2g = 'velocity head'

This is not what I am exploring.

here is a couple of extracts from the British Hydropower Organisation for slow moving fluids under gravity

8.2.3 Gravity Turbines

The Archimedes Screw has been used as a pump for centuries, but in recent decades has also been

operated in reverse as a turbine. It’s principle of operation is the same as the overshot waterwheel, but the

clever shape of the helix allows the turbine to rotate faster than the equivalent waterwheel and with a high

efficiency of power conversion (over 80%). However they are still relatively slow-running machines,

which require a multi-stage gearbox to drive a standard generator.

A key advantage of the Screw is that it is proven to be a ‘fish-friendly’ turbine, so avoids the need for a

fine screen and automatic screen-cleaner because fish and smaller debris can pass safely through the

turbine.

https://british-hydro.org/wp-content/uploads/2023/09/BHA-Micro-Hydro-Guide-2024-3.pdf

Edited 1 hour ago1 hr by studiot